A sinogram warping strategy for pre-reconstruction 4D PET optimization

Abstract

A novel strategy for 4D PET optimization in the sinogram domain is proposed, aiming at motion model application before image reconstruction ("sinogram warping" strategy). Compared to state-of-the-art 4D-MLEM reconstruction, the proposed strategy is able to optimize the image SNR, avoiding iterative direct and inverse warping procedures, which are typical of the 4D-MLEM algorithm. A full-count statistics sinogram of the motion-compensated 4D PET reference phase is generated by warping the sinograms corresponding to the different PET phases. This is achieved relying on a motion model expressed in the sinogram domain. The strategy was tested on the anthropomorphic 4D PET-CT NCAT phantom in comparison with the 4D-MLEM algorithm, with particular reference to robustness to PET-CT co-registrations artefacts. The MLEM reconstruction of the warped sinogram according to the proposed strategy exhibited better accuracy (up to +40.90 % with respect to the ideal value), whereas images reconstructed according to the 4D-MLEM reconstruction resulted in less noisy (down to -26.90 % with respect to the ideal value) but more blurred. The sinogram warping strategy demonstrates advantages with respect to 4D-MLEM algorithm. These advantages are paid back by introducing approximation of the deformation field, and further efforts are required to mitigate the impact of such an approximation in clinical 4D PET reconstruction.

Clinical evaluation of 4D PET motion compensation strategies for treatment verification in ion beam therapy

“…gated 4D PET images) deteriorates the noise break-up effects, which are characteristic for iterative MLEM algorithms due to the ill-posed PET reconstruction problem (Rahmim et al 2013). Drawbacks of both intra-rec warp and post-rec warp have suggested the use of the recently proposed 'pre-reconstruction warping' ( pre-rec warp), which applies the direct motion models on the 4D PET sinograms before reconstruction (Knopf et al 2014, Gianoli et al 2015 (figure 1). The motion models are converted into sinogram domain and the 4D PET sinograms are warped and summed up prior to the simple 3D-MLEM reconstruction of the motion compensated 4D PET reference phase.…”

Initial clinical evaluation of PET‐based ion beam therapy monitoring under consideration of organ motion

“…Improvements are anticipated by 4D MLEM algorithms 22 and sinogramwarping techniques. 36 Beyond low counting statistics, biological washout represents a major challenge. Deviations up to 30% in the absolute activity in fatty tissues and up to 100% in the target volumes have been found and a large interpatient variability observed.…”

PET motion correction in context of integrated PET/MR: Current techniques, limitations, and future projections

“…This method is limited to rigid and affine motion only, mapping straight lines to straight lines. This idea has been extended, by exploiting the fact that straight lines map to sinusoids in the sinogram, to allow for nonrigid motion, a method known as sinogram warping. However, such methods have not gained much attention, possibly due to the complications of transferring motion in “image‐space” to “sinogram‐space”, of which there is no one‐to‐one mapping.…”